JPH07121554B2 - Inspection method for fused part of electrofusion joint - Google Patents

Description

Detailed Description of the Invention Industrial field In recent years, as a pipe joint or saddle joint for plastic pipes used for water and sewer pipes, gas pipes, etc., a heating wire has been buried in the contact surface with the pipe to melt it. BACKGROUND OF THE INVENTION Electrofusion joints have been used in which the welding is performed by energizing a heating wire to heat and melt the contact surface. The present invention relates to an inspection method for finding a defective fusion in a fusion portion with a plastic pipe connected by such a joint.

Conventionally, a device for energizing a joint is conventionally operated manually, and the amount of electricity to be energized has been determined by the operator at the site, that is, by the appearance of the joint at the time of fusion. In recent years, a method has begun to be adopted in which the amount of electric power to be given is set in advance according to the size and type of the joint, and the operator identifies the type based on the appearance of the joint and gives the corresponding amount of electric power. . Regarding recent pipe joints, resistors with different resistance values depending on the type of pipe joint are embedded separately from the heating coil and the resistance value is detected, or the resistance value of the heating coil itself is detected. There is also proposed a method of identifying the type of the above and giving the electric power corresponding to it. Regardless of which method is used, the fused part will have poor fusion strength such as short-circuiting of heating wires, poor contact between the joint and the pipe, insufficient insertion of the pipe in the case of a pipe joint, etc. Sometimes.

Problems to be Solved by the Invention Compared with the former manual method in which the application of electric energy is left to the operator's judgment, the fusion failure as described above is more likely to be overlooked in the latter two methods. 〝Often used for use.

The present invention properly finds a fusion defect and prevents it from being used until a fusion defect occurs.

Solution to Problems The present invention therefore, at the time of or after the completion of the fusing work, a current weaker than the current at the time of fusing is passed through the heating wire to prevent the heating wire from being reheated, and the resistance value or current value at that time. The presence or absence of electrical characteristics such as abnormalities is detected to find defective fusion. Whether or not there is an abnormality in the electrical characteristics can be determined by the operator visually observing the resistance meter or ammeter, but preferably, when there is an abnormality, it can be known by an alarm sound or warning light. desirable.

Action When the heating wire is short-circuited, the resistance value decreases and the current value increases.When the contact between the fitting and the pipe is poor or the pipe is insufficiently inserted in the pipe fitting, the resistance value increases due to the heating of the heating wire and the temperature rise. Is increased and the current value is decreased, so that an abnormality in the fused portion is detected.

Example The drawings show an example of a pipe joint, and the resistance value of the heating coil 2 embedded in the pipe joint 1 varies depending on the type of the joint 1, in other words, the resistance value of the heating coil 2 is detected. By doing so, the type of the pipe joint 1 can be identified. A power amount corresponding to the type of the joint 1 is programmed and stored in the control device 3, the switch 4 controlled by the control device 3 is closed, a current flows from the high voltage source side, and the resistance of the heating coil 2 is increased. When the value is read by a sensor (not shown) and is input to the control device 3, the type of the pipe joint 1 is identified from the input value, and the variable resistor 5 and the variable resistor 5 and The switch 4 is controlled. At the same time when the fusion is completed and the switch 4 is opened by the control device 3 or a little later than that, the switch 6 on the low voltage source side is temporarily closed so that a weak current is supplied to the heating coil 2 for a short time. The resistance value of the heating coil 2 at that time is read by the sensor, is input to the control device 3 and is compared with the resistance value at the normal time, and when it exceeds the normal range, it is judged as abnormal and the alarm lamp is turned on. The alarm circuit 8 for lighting or issuing an alarm sound is closed to issue an alarm.

In the above-mentioned embodiment, the program for detecting the fusion defect is incorporated in the program for giving the electric energy, but in another embodiment, the detecting device is separately provided.

In the above embodiment, the size and type of the joint are identified by energizing the heating coil, and the amount of electric power corresponding to the size and type is provided, but in another aspect, the operator determines the size and type of the joint. Distinguish from the appearance, operate the control device so that the corresponding amount of power is applied, and in other aspects, the fusion work is all done by the operator's judgment, and the abnormality of the fusion part is detected after fusion. Performed by the device.

As described above, the present invention detects the presence or absence of abnormality in the electrical characteristics of the heating wire by flowing a current that is weaker than the fusion current at the time of completion of fusion or after fusion and does not reheat the heating wire. However, because the welding failure is found, the current flowing for inspection is weak, so there is little temperature change of the heating wire itself and it is possible to measure at a substantially constant temperature, improving the measurement accuracy and fusing It is possible to accurately detect the wearing failure.

[Brief description of drawings]

The figure is a schematic view showing an example of a control device used in the method of the present invention. 1 ... Pipe joint, 2 ... Heating coil 3 ... Control device, 4, 6 ... Switch 5 ... Variable resistor, 8 ... Alarm circuit

Claims (2)

[Claims] 1. An electrofusion joint in which a heating wire is embedded in a contact surface with a plastic tube is used, and when the contact surface is fused by heating and melting the contact surface by energizing the heating wire, fusion bonding is performed. When the work is completed or after completion, a current that is weaker than the current at the time of fusion and does not cause reheating is passed through the heating wire, and the presence or absence of abnormality in electrical characteristics such as the resistance value and current value at that time is detected, thus causing fusion failure. A method for inspecting a fusion-bonded portion of an electrofusion joint, characterized in that 2. The method for inspecting a fused portion of an electrofusion joint according to claim 1, wherein the presence or absence of an abnormality in electrical characteristics is displayed by an alarm sound or a warning light.